1. Field of the Invention
The present invention relates to a torque variation absorbing device for an engine.
2. Description of the Prior Art:
An engine for an automobile or an aircraft is equipped with a torque variation absorbing device in the power transmission path.
Known torque variation absorbing devices are disclosed, for instance, in Japanese patent publications SHO 55-20930, SHO 55-20964 and SHO 56-43176. A device of the prior art has two inertia members, i.e., a driving plate which is rotatably connected to an engine crankshaft and a flywheel which is connected to a follower device and is rotatable with respect to the driving plate. Between the driving plate and the flywheel, a spring mechanism and a damping and torque limiting mechanism are installed. In this device the rotation of the engine crankshaft is transmitted to the flywheel through the driving plate, the spring mechanism and the damping and torque limiting mechanism. Thus the torque variation is absorbed by the vibration system of these members.
However, in the above-mentioned device, the damping and torque limiting mechanism is located radially outwardly of the spring mechanism. Therefore, the slip velocity on a slidable part will be increased. As a result, the working life of the device will be reduced.
Further, the driving plate of the device is made from a machined casting which is likely to include cavities. Therefore, the plate must be made thick in order to maintain the structural strength of the plate. Consequently, it was difficult to make the device compact.
The torque variation absorbing device shown in FIG. 7, was developed to solve the above-mentioned problems.
The torque variation absorbing device provides inertia members comprising a driving plate 902 coupled to the engine crankshaft and a flywheel 906 coaxially and rotatably supported on the driving plate 902. The side plate 902c of the driving plate 902 is designed as a separate member from the driving plate bodies 902a, 902b and is fabricated of steel. The steel plate is more reliable in strength than the casting and therefore can be constructed thinner. This thinner designing makes it possible to reduce the axial dimension of the driving plate 902 as compared with the case of a plate machined from a casting.
The periphery 902c' of the opening of the side plate 902c, where the spring mechanism 912 is housed, is bent outwardly in the axial direction by press-working or the like and the spring 913 can be housed even though the thickness of the driving plate 902 is reduced. Thus, the driving plate 902 can be successfully reduced in thickness. The bending of the periphery 902c' is possible, because the side plate 902c is fabricated of steel. Between the driving plate 902 and the flywheel 906 there is interposed a spring mechanism 912 and a damping and torque limiting mechanism 915. In the device, the slidable part of the damping and torque limiting mechanism 915 is located radially inwardly from the spring mechanism 912.
However, this device comprises two driven disks 916, 916 and the cone spring 917 disposed between two driven disks 916, 916. Therefore, the distance between the flange 906d of the driven plate 906b and the center of the end face of the spring mechanism 912 is the sum of the thickness of the lining 916a, the thickness t of the driven disk 916 and the half of the thickness S/2 of the cone spring 917.